This invention relates to a corner member for a spacer strip for the glass panes in a sealed window unit, and particularly for use with the spacer strip as disclosed and claimed in co-pending application Ser. Nos. 512,469, U.S., and No. 437,622 (Canada).
Sealed window units of this type have been known for many years and have become increasingly important and popular as energy conservation and energy efficiency have become more popular. Such a sealed window unit comprises an outer frame or tape supporting the glass panes and a spacer between the glass panes. The spacer is formed in strips which lie along adjacent edges of the panes so as to define a space therebetween and to support the panes in the defined spacing.
To date the most common material which has been commercially used for the spacer in the manufacture of such units has been steel. Steel has been used mainly because it has a co-efficient of expansion similar to that of glass and because this property is the most important in the manufacture of such a unit. It will of course be appreciated that any difference in expansion particularly in climates which have large changes in temperature can have many disastrous consequences, particularly as size of the window increases, including cracking of the glass and at least breaking of the seal between the panes of glass. Other metals such as aluminum are completely unsatisfactory on medium to large windows in that the thermal expansion is very different from that of glass. Similarly many plastics materials such as nylon, vinyl, polythene are available but again these are completely unsatisfactory in view of very different expansion characteristics. To date therefore steel has been the generally accepted material even though this has a number of considerable disadvantages. In particular, the thermal conductivity of steel is considerably higher than that of glass or of the air space between two panes of glass. In a sealed unit heat from within a building tries to escape from a building and the path it takes is through the path of least resistance. In the case of a sealed window unit, the path of least resistance is around the perimeter of the unit where the steel spacer strip is provided. Thus heat is rapidly lost from around the perimeter of the window often causing a ten degrees to twenty degrees farenheit temperature drop at the perimeter of the window relative to the center thereof.
This temperature differential results in differential shrinkage between the center of the glass pane and the perimeter. This can result in a stress crack developing in the glass or can result in the loss of the sealing around the edges of the panes. When the seal breaks down outside air can enter the space between the windows carrying water vapour which is deposited inside the panes causing fogging of the window unit. Approximately five percent of the window units manufactured tend to fail due to such stress cracks, or loss of seal. However it is often thought that the failure is due to shifting of the building rather than to a failure of the window unit itself.
A yet further problem with steel spacer strips is that they are manufactured in certain cut lengths which necessarily cause wastage when cut to specific lengths for use in the window unit. Obviously it is necessary to cut the steel into particular lengths for shipping and handling and of course these lengths cannot be predetermined relative to particular requirements. In addition the finite lengths of the steel strips makes automation of the handling and cutting processes more difficult.
Steel and aluminum spacers of this kind are manufactured by rolling or folding to form a hollow body which is substantially rectangular in cross-section with a slot or interlock along the upper surface between the two folded edges of the steel strip from which the folded body is formed. It is important to maintain the width of the slot as narrow as possible in order to allow the ingress of air from the space between the window panes while preventing the escape of granular dessicant material. In manufacture of a window unit using the spacer, dessicant is added into the interior of the hollow spacer so as to dry out the air remaining between the panes of glass so that no water is condensed onto the inside faces of the glass thus fogging the window unit. Steel which is very unsuitable for extrusion processes can however be readily formed by a folding process into a shape of this type. However folding processes are limited in the type of shape that can be formed.
In the above applications there is disclosed a spacer strip formed from a pultruded glass fibre reinforced material which provides a number of improvements relative to the prior art steel arrangement.
However, one particular problem arises in the use of a pultruded glass fibre reinforced material in that the material is less rigid than the conventional steel strip and therefore the conventional design of corner member whereby four of the strips are interconnected at right angles to form a rectangular spacer for the outside of the sealed window unit causes problems. Specifically the conventional corner member acts to open the slot in the pultruded glass fibre reinforced spacer strip so as to deform the strip with the danger of the dessicant escaping and also losing the accurate linearity which is required to seal against the glass panes.
It is one object of the present invention, therefore, to provide a corner member for use with a spacer strip of this type.
According to the invention, therefore, there is provided a corner member for joining spacer strips of a sealed window unit, the spacer strips each comprising a hollow elongate body of substantially rectangular crosssection providing two side surfaces for contacting and spacing adjacent surfaces of glass panes, an outer surface for facing outwardly of the outer edge of the glass panes and an inner surface for facing inwardly toward opposed spacer strips of the sealed window unit, the inner surface having a slot extending along the full length thereof, the corner member comprising a pair of legs arranged right angles, each of the legs being dimensioned so as to be received within the hollow body of one of the spacer strips in a compression fit, the leg being shaped and arranged such that the compression fit is limited to areas of the spacer strip adjacent junctions thereof between the sides and the outer surface whereby the compression does not cause opening of the spacer strip at the slot in the inner surface.
Preferably the compression fit at the confined areas is provided by a pair of lateral projections on the sides of the leg. These lateral projections can be defined by side surfaces converging to a sharp edge longitudinal of the leg and inclined outwardly and downwardly.
The invention also includes a combination of the corner member with spacer strips preferably of the above type wherein the junctions between the sides and outer surface of the spacer strip include co-operating recesses for receiving lateral projections of the legs of the corner member.
In this way all of the compression force or substantially the whole of the compression force is taken up in the outer surface without applying substantial bending moments to the sides about the junction and thus avoiding opening of the part at the slot in the inner surface.
With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the best mode known to the applicant and of the preferred typical embodiment of the principles of the present invention, in which: